Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$13.33	9.851%	$14.6431	$14.64	$14.65	$14.60
Purchase #2	$245.90	5.666%	$259.8327	$259.83	$259.85	$259.80
Purchase #3	$118.89	12.141%	$133.3244	$133.32	$133.30	$133.30
Purchase #4	$21.95	4.196%	$22.871	$22.87	$22.85	$22.90
Purchase #5	$216.38	11.435%	$241.1231	$241.12	$241.10	$241.10
Purchase #6	$181.47	8.465%	$196.8314	$196.83	$196.85	$196.80
Purchase #7	$189.30	7.700%	$203.8761	$203.88	$203.90	$203.90
7 purchase totals =	$987.22		$1,072.5018	$1,072.49	$1,072.50	$1,072.40